The current 5-year survival rate for of lung cancer is 16% in developed countries. In part this is because lung cancer tends to present late and there is no effective early screening programme. There is therefore a need for a low cost, non-invasive, entirely safe screening means for selecting individuals with predicted lung lesions which can be applied by non-specialist staff with the aim of improving early presentation for lung cancer diagnosis and thereby lung cancer survival rates.
In order to have an effective screening programme for lung cancer diagnosis, tumours need to be identified at the T1 (3 cm or less diameter), N0, M0 stage (i.e. before nodal involvement and before the tumour has metastasised). Surgical resection is usually possible at this stage achieving a complete cure.
A fast response ion-exchange humidity sensor that responds in real time to water vapour in a gas stream is disclosed in Published International Application WO 2008/009980 (in common ownership with the present application). The thin layer of ion exchange material extending between the working electrode and the counter electrode of this form of sensor comprises a sulphonated tetrafluoroethylene copolymer (conveniently and preferably Nafion®, available commercially from Du Pont). The humidity profile of serial exhaled breaths can be measured by providing an inlet such that dry gas is directed on to the sensing element during inhalation through the sensor. The sensor is thereby returned to its pre-test state almost instantly. As taught by related published US Application 2008-026370A1, resultant humidograms can be directly correlated with respiratory function and may, for example, be used to assess deterioration of respiratory function associated with respiratory diseases such as asthma.
During the course of preliminary trials of such a device to assess respiratory function, it was surprisingly observed by the inventors that the humidograms occasionally exhibited an irregularity (an indent) in the Phase II initial upward curve portion when compared to the expected profile. Further check on the health of relevant subjects revealed lung cancer.
Most patients with lung cancer come from a population with chronic respiratory symptoms. If smokers were to be referred for imaging every time a new respiratory symptom appears, as some advise, then the healthcare infrastructure would be ill-equipped to cope with demand and this could be seen as an inefficient use of resources. The lack of availability of suitable screening tools to aid decision making on referral for confirmatory lung cancer diagnosis and treatment is thus a constant cause of frustration for oncologists.
There are three leading technologies that are being actively researched as potential screening tools: computed tomography (CT), mass spectrometry and electronic nose technology. CT scanning has been investigated extensively as a potential screening tool. CT scanning presents difficulty in picking up sufficient tumours to justify screening as routine; there is high financial cost and limitations on CT facilities. In addition, the risk of radiation-induced cancers (estimated at 1 fatality per 1300 patients scanned) makes this an unsuitable large scale tool. ‘Electronic nose’ technology with gas chromatography is a technology that is also being investigated. However, even with highly sensitive machines, no true specificity has been demonstrated and again the high cost of such technology is a problem.